1. Field of the Invention
The present invention relates to biological soil improvement products and methods for their application to soil.
2. Description of the Prior Art
Certain Azospirillum and Bacillus bacteria are known to be useful as nitrogen-fixing organisms for plants in soil [Japanese Patent No. 60- 051684 and Russian Patent No. 1,210,383.]. It is also known that Bacillus polymixa possesses anti-bacterial activity, particularly against Gram negative bacteria.
Microorganisms have been employed in soil treatments as far back as the last century. See, e.g., "Bacteria In Relation to Country Life," J. Lipman, MacMillan Co., New York (1912); and "The Micro-Organisms of the Soil," Sir E. John Russell, Longmano, Green & Co., London (1923). However, this use consisted for the most part of the one or two specific microorganisms or a "grab bag" mixture of soil cultures that were not specifically identified or quantified. Some were nothing more than composted manures carrying groups of microorganisms typically found in such waste. The beneficial activity of such unquantified mixtures on the soil resulted in increased crop yields. More recently, there have been more sophisticated microbial formulations and specific characteristics of individual formulations documented. See, e.g., "Biological Control of Plant Pathogens," K. Baker et al., W. H. Freeman & Co., San Francisco (1974); "Beneficial Bacteria Enhance Plant Growth," T. Suslow et al., U. California Dir. Agri. St. Reports, California Agriculture, Vol. 33, No. 11-12, pp. 15-17 (Nov./ Dec. 1979); and "Microbial Interactions in Soils and Health Plant Growth," A. M. Smith, Australian Plant, Vol 9, No. 73, pp. 209-212 (Dec. 1977).
However, actual use of specific groups of organisms on plants met with varying degrees of success depending on other non-controlled variables. Such variables include: (1) the presence of absence of adequate micro- and macro-nutrients in the soil to support the propagation of the microorganisms; (2) the amount of organic material able to hold nutrients and microbes to create a suitable environment for microbial growth; and (3) the presence or absence of certain minerals required by the plant for proper uptake of the nutrients provided by the microbial activity.
It is an object of the invention to provide an improved biological product for improving the plant growth capability of soil which synergistically combines the activities of specific Azospirillum and Bacillus bacteria.